Cellana grata is a high-zoned, exposed-shore limpet with a lifespan of 3 years. Patclloida pygmaeais a low-zoned, sheltered-shore limpet with a lifespan of I year. C. grata migrates up-shore in winter, but occurs lower on the shore in summer. This migration is synchronized with variations in algal availability high on the shore; such variations are, however, themselves related to seasonal changes in wave height. P. pygmaea is restricted to the low shore, year round. The movements upwards in winter and downwards in summer are still evident. Algal species richness increased from September to reach a peak between December and March, and to abruptly diminish between May and June. The encrusting algae Brachytrichia maculans, Hildenbrandia prototypus, Lithothamnion sp. and Ralfsia vcrrucosa were present year round. The timing of juvenile recruitment of C. grata and P. pygmaea was from October to July and February to October, respectively. Temperature may be important in enhancing juvenile survival by affecting the seasonal pattern of algal occurrence on the shore. Seasonal fluctuations in the rate of growth were recorded for both species with the time of fastest growth of C. grata and P. pygmaea occurring between October and March and September and February, respectively. Mortality of both species occurred mainly in summer. Summer heat, predation and intra-specific competition for food appear to be the major causes of death.